<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    table{
       width: 200px;
      height: 50px;width: 200px;
      height: 50px;
      margin: 0 auto;
    }
    table,
    td{
      border: 1px solid gray;
      /* collapse合并单元格 */
      border-collapse: collapse;
      text-align: center;
      line-height: 50px;
      
    }
  </style>
</head>
<body>
  <!-- 
  header,footer,article,footer,section,nav,mark,progress,meter
  number,boolean,string,null,undefinded
  border-radius,box-shadow,border-image
  元素选择器，类选择器，id选择器，属性选择器，通用选择器，后代选择器，子代选择器
  -->
  <table>
    <tr>
      <td>姓名</td>
      <td>语文</td>
      <td>数学</td>
    </tr>   

     <tr>
      <td>张三</td>
      <td colspan="2>123</td>
      <td ">123</td>
    </tr>  

     <tr>
      <td>李四</td>
      <td>321</td>
      <td>123</td>
    </tr>

  </table>
</body>

</html>